This section is adapted from the book, Triathlon Training in Four Hours a Week: From Beginner to Finish Line in Just Six Weeks, by Eric Harr
1. Choose your starting position wisely. If the triathlon you've entered has a mass start (meaning all racers start at the same time) rather than starting in age-group waves, place yourself in the crowd according to your goals and ability. If you're a beginner who's there just to finish, start in the back so you don't get trampled. Likewise, if you're a strong swimmer and a contender, begin in the front of the pack so you don't end up trampling those in front of you.
2. Do not draft on the bike. Unless you are competing in a "draft legal" event (which isn't likely), you cannot follow behind another cyclist to gain a drafting advantage. You can draft only in the swim and the run. Stay at least 10 bike lengths behind the rider in front of you.
3. Keep your helmet buckled whenever you're touching your bike. This means before you unrack it after the swim leg and until you rerack it after the bike leg. Take this rule very seriously you can be disqualified for violating it.
4. Do not cross the center line. This speaks for itself. People have been killed crossing the center line during the bike leg of the triathlon. I don't care how competitive you are or how fast you want to go, never, ever do it.
5. Be aware of others. This is particularly important on the bike. Nobody wants road rash. Stay aware at all times.
6. Treat the volunteers with courtesy and respect. Thank them when they give you water during the race, and follow their instructions without griping if they ask you to do something like head to the swim start early.
7. Avoid the urge to go nude. You'd be amazed at what some people will do in transition areas! I've seen some seriously naked people over the years, and though they invariably give me a good laugh, the officials don't find them so funny.